Indeed.. 500 segments won't get you very far. However, something to consider
when looking at paying for modeling tools (nec4win, eznec, HFSS, Symphony,
etc.) is that if you are investing $10k in multiple antennas and towers and
assembly and installation cost (be fair, count your own time involved),
spending a few hundred dollars on an appropriate tool may be a good
investment.
Sometimes what you're paying for is support or a user interface that YOU
find easy to use for YOUR specific problems(lots of different modeling
programs around, and they all have different user interface philosophies).
For instance, I started using 4nec2 because a)it was free and b) it parsed
the raw NEC output files into POVray images of the pattern, for which I had
a need at the time. I am quite facile with generating the NEC input decks
(which, in my case, usually are generated by some other program anyway), so
the nifty geometry entry capabilities of some of the other programs aren't
as useful.
Likewise, as Pete, mentioned, MultiNEC has the really, really useful feature
of converting between the various forms of model description.
On the other hand, programs like EZ-NEC are much easier for defining the
geometry, and, have user interfaces that are more structured and facile for
the average ham. If you like the interface, and you need 1000's of segments
(which you would, if you're trying to do a high quality model with
environmental stuff and interactions, as opposed to, say, free space models
of the antenna by itself), it's probably worth coming up with the cash for
the pro version.
I should also mention that for large models, some of the commercial versions
run faster than the off-the-web free versions. Faster matrix math
libraries, support for multiple processors or clusters, better optimization
algorithms, etc. If time is money (as it is, when you're getting paid to do
the analysis work), then cutting iteration time down can be worth a lot.
Some other resources on electromagnetic modeling are the Applied
Computational Electromagnetics Society (ACES) which has a web site at
University of Missouri, and the JPL EMLIB web site
http://emlib.jpl.nasa.gov/
----- Original Message -----
From: "Pete Smith" <n4zr@contesting.com>
To: "Jim Lux" <jimlux@earthlink.net>; "Chuck Dietz" <w5pr@swbell.net>; "Gary
R." <n6lrv@arrl.net>; <towertalk@contesting.com>
Sent: Sunday, November 09, 2003 2:21 PM
Subject: Re: Windows based NEC programs was Re: [TowerTalk] K6STI YO / AO
Programs?
> At 02:17 PM 11/9/03 -0800, Jim Lux wrote:
> >EZ-NEC is a well respected Windows version of NEC.
>
>
> The big problem with EZNEC, unfortunately, is that unless you buy the pro
> version for much more money it has a limit of 500 segments. Try modeling
a
> single-tower station on 10 or 15 meters, looking for interactions with all
> the other conductors (antennas, guys, etc.) and you'll quickly find this a
> difficult limitation to live with.
>
> I should add that I use 4NEC 2 in conjunction with MultiNEC, because the
> latter does not provide antenna viewers, while the latest evolution of
> 4NEC2 has a really neat Direct X antenna pattern and geometry viewer. I
> have imported all of my EZNEC modeling files into MultiNEC; one of the
very
> neat things MultiNEC does is to translate among the proprietary formats of
> the various other Windows-based programs, as well as vanilla NEC.
>
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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